1979 70hp Johnson

[Mancil Russell]

My motor runs good at near sea level altitudes but would only rev up to 2200 rpm at a lake that was 4800 ft up are the carbs supposed to do something for altitude automatically? or is there an adjustment? I have a Seloc tech manual that says nothing either way
I tested it by pulling the boat out of the 4800 foot lake this morning and driving 70 miles to a near sea level lake and it worked fine (turned up to 5000rpm) the drive was about a 1 1/2 hour.
I also ran it all last weekend at a near sea level lake with no problems but for 3 days at the High lake nothing more then 2200rpms

 

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Re: 1979 70hp Johnson

I think you have a different problem other then the change in altitude. My 9.9 is ran at sea level and in the mountains at about 3000 feet all summer long. I don't think you can even realize the change.

 

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Re: 1979 70hp Johnson

Forgot to say rest of my thought. You would have to re-jet the carbs to compensate for altitude if that were the case. You would have to lean it out some, but like I said I dout if that is the case.